Bukhari mentions in his ‘Saheeh’ from Wahab bin Munnabih that it was said to him: ‘Is not ‘La ilaha ‘illa Allaah’ the key to Paradise?’

He said: ‘Of course, however there is no key except that it has teeth, so if a key is brought which has teeth then it will be opened, otherwise it will not open.’

Ibn Qayyim continues:

‘Allaah Subhanahu has placed keys for everything that is necessary, and they open the way, so Allaah made purification the key for prayer, as the Messenger –sallAllaahu alayhi wa sallam– said: ‘The key to prayer is purification.’ [Saheeh al-Jamia as-Sagheer No.5885]

Like wise Ihram is the key to Hajj,

Truthfulness is the key to righteousness,

Tawheed is the key to Paradise,

Asking good questions and being attentive is the key to knowledge,

Patience is the key to victory and triumph,

Gratitude is the key to increase of provision,

Remembrance of Allaah is the key to having loyalty to Allaah and His love,

Taqwa (piety) is the key to success,

Fervent desire and dread of Allaah is the key to being successful,

Dua’ (Supplicating) is the key to being responded to,

Zuhd (Abstaining from the luxuries of the world) is the key to desiring the Hereafter,

Reflecting about that which Allaah calls His slaves to is the key to Eemaan (having faith),

Making the heart accept Islaam and making it secure for Allaah and having sincerity for Him by having love and hate and fulfilling His commands and leaving the prohibitions is the key to going in front of Allaah,

Pondering upon the Qur’aan, and imploring Allaah before dawn and not sinning is the key to giving the heart life,

Being kind to the worshippers of the Creator and striving to benefit His worshippers is the key to obtaining mercy,

Striving to seek forgiveness from Allaah and Taqwa (piety) is the key to Rizq (provisions),

Obedience to Allaah and His Messenger is the key to honour,

Longing for the Hereafter is the key to being prepared for the Hereafter,

Fervent desire for Allaah and the Hereafter is the key to all goodness,

Love for the world, continuously longing for it and turning away from the Hereafter is the key to all evil.

This is a great matter from the most beneficial chapters of knowledge, namely knowing the keys to goodness and evil.’

'‘Whoever sleeps while in a state of purification then an Angel spends the night in his garment, he does not wake up at any time during the night except that the Angel says: O Allaah forgive Your slave such and such since he went to sleep upon purification.’'

[Collected by Abdullaah ibn al-Mubarak in 'Hadeethihi' & 'Zuhd', and Albaani declared it to have a Hasan Isnaad in Silsilah Saheehah no. 2539]